Method for transmitting digital useful data

ABSTRACT

The method for transmitting useful digital data from a first ( 1 ) to a second mobile station ( 5 ) saves computing costs and prevent data loss. In this method for transmission in a first network ( 10 ), the first station ( 1 ) source encodes useful data in a first step and then channel encodes the source encoded useful data in a second step. The encoded useful data are transmitted as a first bit stream to an intermediary station ( 15 ) via a transmission channel of the first network ( 10 ). The encoded useful data in the first bit stream are channel decoded by the intermediary station ( 15 ). For transmission in a second network ( 20 ), the useful data are again channel encoded by the intermediary station ( 15 ) and are transmitted to a second mobile station ( 5 ) via a transmission channel of the second network ( 20 ). Signalization data containing information regarding the encoding in the first step are transmitted from the intermediary station ( 15 ) to the second mobile station ( 5 ). The useful data coded in the second step are channel decoded by the second mobile station ( 5 ). The resulting channel decoded useful data are then source decoded by the second mobile station ( 5 ) according to signalization data received by the second mobile station ( 5 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for transmitting useful digital datafrom a first mobile station to a second mobile station.

2. Prior Art

Method for transmitting useful digital data from a first mobile stationto a second mobile station are already known and are embodied for voicetransmission, for example, in accordance with the GSM standard (GlobalSystem for Mobile Communications).

EP 0 849 965 A1 has disclosed a telephone device, which can telephone ina particularly advantageous manner in enclosed spaces via both anexisting mobile radio network and a fixed telecommunication network withthe aid of a dual-mode base station. The dual-mode base station, whichcan also be referred to as a twin station, has a DECT charging stationand a DCS/GSM charging station with a voice interface. By plugging theDCS/GSM mobile station into the dual-mode base station, the mobilestation is given the ability to receive mobile radio signals. Thesemobile radio signals are then converted into DECT signals. Theconnection to the DECT mobile phone is then established via a DECTantenna. In a similar manner, the PSDN/ISDN signals are also convertedand emitted via DECT.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved methodof transmitting useful digital data between mobile stations.

The method according to the invention has advantages has the followingadvantageous features: that for the transmission in a firsttelecommunication network, the first mobile station encodes, preferablysource encodes, the useful data in a first step and encodes, preferablychannel encodes, the useful data in a second step, that the useful dataencoded in the first and second steps are transmitted in the form of afirst bit stream to an intermediary station via a transmission channelof the first telecommunication network, in particular via at least onethird telecommunication network, that the useful data of the first bitstream are decoded, preferably channel decoded, by the intermediarystation in the second step, that for the transmission in a secondtelecommunication network, the useful data are encoded, preferablychannel encoded, by the intermediary station in the second step, thatthe useful data are transmitted to the second mobile station via atransmission channel of the second telecommunication network, thatsignalization data are transmitted from the intermediary station to thesecond mobile station, wherein the signalization data containinformation regarding the type of encoding of the useful data in thefirst step, that the useful data are decoded, preferably channeldecoded, by the second mobile station in the second step, and that theuseful data decoded by the second mobile station in the second step aredecoded, preferably source decoded, by the second mobile station in thefirst step, depending on the signalization data received by the secondmobile station. In this manner, the useful data received in theintermediary station are only decoded in the second step, but not in thefirst step. Then an encoding in the first step for the transmission ofthe useful data in the second telecommunication network is notnecessary. A decoding in the first step of the useful data received inthe second mobile station can then take place through the evaluation ofthe signalization data transmitted along with the useful data by theintermediary station. A transcoding between different codes for theencoding in the first step for transmission in the respectivetelecommunication network can consequently be avoided, which can savecomputing costs and prevent the lost of useful data that occurs during atranscoding.

Advantageous improvements and updates of the method disclosed in themain claim are possible through the measures taken in the dependentclaims.

It is particularly advantageous that the useful data in the firsttelecommunication network are transmitted in accordance with a firstmobile radio standard, in particular in accordance with the GSM standard(Global System for Mobile Communications), encoded, preferably sourceencoded and channel encoded, in the first and second step, that theuseful data in the second telecommunication network are encoded,preferably channel encoded, in the second step and are transmitted inaccordance with a second mobile radio standard, in particular inaccordance with the UMTS standard (Universal Mobile TelecommunicationsSystem), together with the signalization data, which include informationregarding the encoding of the useful data in the first step inaccordance with the first mobile radio standard, and that the usefuldata, which are decoded, preferably channel decoded, by the secondmobile station in the second step, are decoded, preferably sourcedecoded, by the second mobile station in accordance with the firstmobile radio standard after the evaluation of the signalization data. Inthis manner, useful data can be transmitted between mobile stations witha respective air interface embodied according to a different mobileradio standard without which a transcoding of the useful data withregard to the code for the encoding in the first step would be required,provided that the second mobile station which receives the useful datais in a position to execute a decoding of the received useful data inthe first step in accordance with the first mobile radio standard.

DRAWING

An exemplary embodiment of the invention is shown in the drawing andwill be described in detail in the subsequent description.

The sole FIGURE is a block circuit diagram for the transmission ofuseful data from a first mobile station. to a second mobile station viaan intermediary station by means of different telecommunicationnetworks.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT

In the FIGURE, the reference numeral 1 indicates a first mobile station,which is embodied in accordance with a first mobile radio standard. Thefirst mobile radio standard can, for example, be the GSM standard(Global System for Mobile Communications). The first mobile station 1will be referred to below as a GSM mobile station. The FIGURE shows onlythose functional blocks of the first mobile station 1 that are requiredfor the description of the method according to the invention. The firstmobile station 1 includes an encoder 25 embodied as a source encoder foran encoding in a first step which encoder is embodied in accordance withthe first mobile radio standard, the GSM standard in the exampledescribed. By means of a first encoder 35 embodied as a channel encoderfor an encoding in a second step, which encoder is likewise embodied inaccordance with the first mobile radio standard, the source encoder 25is connected to a first send-receive unit 40, which is connected to afirst send-receive antenna 45. Radio signals can be transmitted by thefirst send-receive antenna 45 to a second send-receive antenna 50 of anintermediary station 15 in accordance with the first mobile radiostandard by means of a first telecommunication network 10 which isembodied as a GSM network in the exemplary embodiment described. Theintermediary station 15 contains a second send-receive unit 55, which isconnected to the second send-receive antenna 50. The second send-receiveunit 55 is connected to a first decoder 60 embodied as a channel decoderfor a decoding in the second step, which is connected to a control unit65 of the intermediary station 15. By means of a second encoder 70embodied as a channel encoder for the encoding in the second step, thecontrol unit 65 is connected to a third send-receive unit 75 of theintermediary station 15, which is connected to a third send-receiveantenna 80. The third send-receive antenna 80 transmits radio signals toa second mobile station 5 in accordance with a second mobile radiostandard by means of a second telecommunication network 20. The secondmobile radio standard can, for example, be the UMTS standard (UniversalMobile Telecommunications System). For the intermediary station 15 aswell, the FIGURE shows only the functional blocks required for thedescription of the method according to the invention. The same is truefor the second mobile station 5, which receives the radio signals fromthe intermediary station 15 by means of a fourth send-receive antenna85. The second mobile station 5 includes a fourth send-receive unit 90which is connected to the fourth send-receive antenna 85. The fourthsend-receive unit 90 is also connected to a second decoder 95 embodiedas a channel decoder for the decoding in the second step, which isconnected to an evaluation unit 100. By means of a switch 105 that canbe controlled by the evaluation unit 100, the second channel decoder 95is connected either to a first decoder 30 embodied as a source decoderfor a decoding in the first step or to a second decoder 110 embodied asa source decoder for the decoding in the first step. The first sourcedecoder 30 is embodied in accordance with the first mobile radiostandard and the second source decoder 110 is embodied in accordancewith the second mobile radio standard. In the following, the UMTSstandard has been selected by way of example for the second mobile radiostandard so that the second mobile station 5 is at least partiallyembodied as a GSM/UMTS mobile station. The source encoder 25 is suppliedwith useful digital data, which can be video data, audio data, textdata, voice data, and/or any other data. In the following, thetransmission of useful data between the first mobile station 1 and thesecond mobile station 5 will be described by way of example inconjunction with the transmission of voice data. The source encoder 25is then embodied as a voice encoder according to the first mobile radiostandard, the GSM standard in this example. As a result, the voiceencoder 25 can be based on the GSM standard ITU-T G. 729. The voiceencoder 25 executes a source encoding of the useful data, which aresupplied to it and are embodied as voice data, in accordance with theGSM standard. The voice data source encoded in this manner are suppliedto the first channel encoder 35, which executes a channel encoding ofthe voice data, for example a folding encoding and a block encoding, inaccordance with the GSM standard. The voice data source encoded andchannel encoded in this manner are then transmitted via the firstsend-receive unit 40 from the first send-receive antenna 45 to theintermediary station 15 in the form of a first bit stream by means of afirst transmission channel of the first telecommunication network 10embodied as a GSM network. The bit stream received by the secondsend-receive antenna 50 is then supplied to the first channel decoder 60via the second send-receive unit 55. The first send-receive antenna 45,together with the second send-receive antenna 50, thereby constitutes aso-called GSM air interface. The source encoded and channel encodedvoice data of the first bit stream are then channel decoded in the firstchannel decoder 60 in accordance with the GSM standard. The voice datachannel decoded in this manner are then source encoded again and aresupplied to the control unit 65. Along with the voice data, the firstmobile station 1 has also transmitted call identification data to theintermediary station 15, which identify the second mobile station 5 asthe targeted subscriber for the voice data to be transmitted. These callidentification data have been generated, for example, in a control unit,not shown in the drawing, of the first mobile station 1, are channelencoded by the first channel encoder 35, and are transmitted along withthe voice data to the intermediary station 15 in the first bit stream.Together with the voice data, these call identification data are thenalso channel decoded by the first channel decoder 60 and likewisesupplied to the control unit 65. The call information data can also betransmitted from the first mobile station 1 to the intermediary station15 singly or multiply via a separate control channel, separate from thevoice data and include the telephone number of the second mobile station5 as the target station. The control unit 65 detects these callidentification data and based on these data, designates the secondmobile station 5 as the target subscriber for the voice data to betransmitted from the first mobile station 1. In this connection, it isknown in the control unit 65 that in order to transmit the voice datafrom the intermediary station 15 to the second mobile station 5, atransmission channel must be established in the second telecommunicationnetwork 20. The transmission of voice data in the secondtelecommunication network 20 occurs in accordance with the second mobileradio standard, the UMTS standard in the exemplary embodiment described.The third send-receive antenna 80 and the fourth send-receive antenna 85consequently constitute a UMTS air interface. It is also known in thecontrol unit 65 that the intermediary station 15 can decode both usefulsignals source encoded in accordance with the GSM standard and usefulsignals source encoded in accordance with the UMTS standard. The controlunit 65 therefore selects a data transmission service in accordance withthe UMTS standard in which the voice data, which have been channeldecoded but are still source encoded in accordance with the GSMstandard, are embedded in a second bit stream in accordance with theUMTS standard.

The intermediary station 15 can also have the potential for a sourcedecoding of received useful data in accordance with the GSM standard. Inthis instance, along with the call identification data, it is useful toalso transmit, for example, the telephone number of the calling firstmobile station 1 to the intermediary station 15 and to forgo a sourcedecoding of the received useful data in the intermediary station 15depending on the detection of this telephone number in the control unit65.

The control unit 65 also embeds signalization data into the second bitsteam, wherein the signalization data contains information regarding thetype of source encoding of the useful data. The signalization dataconsequently indicate that the useful data in the form of voice data inthe example described are source encoded according to the GSM standard.In the second channel encoder 70, the voice data and the signalizationdata of the second bit stream are channel encoded according to the UMTSstandard for transmission in the second telecommunication network 20,for example likewise by means of a folding encoding and a blockencoding. The third send-receive unit 75 transmits the thus channelencoded voice data and signalization data of the second bit stream tothe second mobile station 5 via a transmission channel of the secondtelecommunication network which in this example, is embodied as a UMTSnetwork. With the data transmission service selected by the control unit65 in accordance with the UMTS standard, the transmission quality andthe transmission data rate must be suitably selected in order totransmit the voice data which is still source encoded in accordance withthe GSM standard. The second bit stream with the voice data andsignalization data, which are channel encoded in accordance with theUMTS standard, is received by the fourth send-receive antenna 85 and issupplied to the second channel decoder 95 by means of the fourthsend-receive unit 90. The second channel decoder 95 executes a channeldecoding of the voice data and the signalization data of the second bitstream in accordance with the UMTS standard. The evaluation unit 100detect the channel decoded signalization data which do in face containknown information regarding the type of source encoding of the receivedvoice data of the second bit stream. In the current example, theevaluation unit 100 extracts from the channel decoded signalization dataof the second bit stream the fact that the voice data of the second bitstream are source encoded in accordance with the GSM standard. Theevaluation unit 100 therefore triggers the switch 105 in such a way thatthe second channel decoder 95 is connected to the first source decoder30, which is embodied as a voice decoder in accordance with the GSMstandard. For the case in which the evaluation unit 100 extracts fromthe received and channel decoded signalization data of the second bitstream the fact that the voice data of the second bit stream are sourceencoded in accordance with the UMTS standard, it triggers the switch 105in such a way that it forms a connection—as depicted with dashed linesin the FIGURE—between the second channel decoder 95 and the secondsource decoder 110, which is then embodied as a voice decoder inaccordance with the UMTS standard. According to the exemplary embodimentdescribed, since the voice data of the second bit stream are sourceencoded in accordance with the GSM standard, the second channel decoder95 is connected to the first voice decoder 30 and the voice data channeldecoded in the second channel decoder 95 are source decoded in the firstvoice decoder 30. The channel decoded and source decoded voice signalspresent at the output of the first voice decoder 30 and the second voicedecoder 110 are then supplied for further processing to additionalfunction blocks not shown in the FIGURE.

The signalization data can also be transmitted from the intermediarystation 15 to the second mobile station 5 singly or multiply via aseparate control channel separate from the useful data and in turn caninclude the telephone number of the first mobile station 1 making thecall, by means of which the evaluation unit 100 can likewise be inducedto connect the first voice decoder 30 to the second channel decoder 95.

In lieu of or in addition to the voice data, at least video data and/oraudio data and/or text data can also be transmitted as useful data fromthe first mobile station 1 to the second mobile station 5 in the mannerdescribed above and combined into one bit stream. The transmission inthe first telecommunication network 10 and in the secondtelecommunication network 20 can take place, for example, in a frequencymultiplexed or time multiplexed manner, wherein different multiplexingmethods can be used for the two different telecommunication networks 10,20. In this instance, for example, a conversion from time multiplexingto frequency multiplexing or vice versa would also have to be achieve inthe intermediary station 15. Arbitrary other multiplexing or channelaccess methods can also be used.

With the method according to the invention, it is consequently possible,for example, to transmit useful data that are source encoded accordingto the GSM standard via a data connection according to the UMTSstandard. In this manner, a request for the UMTS standard as the mobileradio standard of the third generation can be fulfilled to assure abackwards compatibility to the existing GSM standard as the mobile radiostandard of the second generation in order to exchange useful databetween GSM standard mobile stations and UMTS standard mobile stationsvia a mobile radio connection. The method according to the inventionsimplifies the transmission of useful data between mobile stationsembodied in accordance with the GSM standard and those mobile stationsthat are embodied in accordance with both the GSM standard and the UMTSstandard, wherein the UMTS air interface is used for the part of thedata transmission from the corresponding telecommunication network tothe mobile station that is embodied in accordance with both the GSMstandard and the UMTS standard. As a result, the useful data in themobile station that is embodied in accordance with both the GSM standardand the UMTS standard are of a quality that has not been reduced by atranscoding between a GSM standard source code and a UMTS standardsource code.

The first telecommunication network 10 and the second telecommunicationnetwork 20 can each be embodied as a hybrid GSM/UMTS network whichcombines the functions of a GSM network and a UMTS network. The firsttelecommunication network 10 and the second telecommunication network 20can also be identical.

The provision can also be made that the useful data from the firsttelecommunication network 10 can be transmitted via one or a number ofarbitrary fixed networks and possibly via corresponding intermediarystations, to the second telecommunication network 20 and from there, onto the second mobile station 5, wherein a transcoding with regard to thesource code of the useful data, i.e. a source decoding and new sourceencoding in the corresponding intermediary stations does not occur, butonly a channel decoding and possibly, a new channel encoding.

For example, the standard IS95 provided in North America (InterimStandard 95), the PDC standard provided in Japan (Personal DigitalCellular), or the like can also be selected as the first mobile radiostandard.

1. A method for transmitting useful data from a first mobile station (1)to a second mobile station (5), in which for transmission in a firsttelecommunication network (10), the first mobile station (1) sourceencodes useful data in a first step and then channel encodes the usefuldata in a second step; the useful data encoded in the first and secondsteps are transmitted in the form of a first bit stream to anintermediary station (15) via a transmission channel of the firsttelecommunication network (10); the useful data channel encoded in thesecond step presented in the first bit stream are channel decoded by theintermediary station (15); for transmission in a secondtelecommunication network (20), the useful data are channel encoded bythe intermediary station (15) and the useful data thus channel encodedare transmitted to a second mobile station (5) via a transmissionchannel of the second telecommunication network (20), signalization dataare transmitted from the intermediary station (15) to the second mobilestation (5), said signalization data containing information regardingthe type of encoding of the useful data in the first step, the usefuldata channel encoded in the intermediary station are channel decoded bythe second mobile station (5), and then the useful data channel decodedby the second mobile station (5) are source decoded by the second mobilestation (5), according to the signalization data received by the secondmobile station (5).
 2. The method according to claim 1, wherein theuseful data encoded in the first and second steps are transmitted in theform of said first bit stream to said intermediary station (15) via atleast one third telecommunication network.
 3. The method according toclaim 1, wherein the signalization data are added to the useful datachannel decoded in the intermediary station (15) so that a second bitstream is produced for the transmission in said second telecommunicationnetwork (20), the useful data and the signalization data of the secondbit stream are channel encoded by the intermediary station (15); theuseful data and the signalization data of the second bit stream aretransmitted to the second mobile station (5) via transmission channel ofthe second telecommunication network (20); the useful data and thesignalization data of the second bit stream are channel decoded by thesecond mobile station (5) and then the useful data, which are channeldecoded in the second step by the second mobile station (5), are sourcedecoded by the second mobile station (5) according to the signalizationdata decoded by the second mobile station (5).
 4. The method accordingto claim 1, wherein the useful data in the first telecommunicationnetwork (10) are transmitted in accordance with a first mobile radiostandard; the useful data are source encoded and channel encoded in thefirst and second step respectively, the useful data in the secondtelecommunication network are channel encoded and are transmitted inaccordance with a second mobile radio standard together with thesignalization data, said signalization data include said informationregarding the type of encoding of the useful data in the first step inaccordance with the first mobile radio standard; and wherein the usefuldata coded in the second step, which are decoded by the second mobilestation (5), are decoded by the second mobile station (5) in accordancewith the first mobile radio standard after evaluating the signalizationdata.
 5. The method according to claim 4, wherein said first mobileradio standard is a global system for mobile communications and saidsecond mobile radio standard is universal mobile telecommunicationssystem.
 6. The method according to claim 4, wherein the useful data inthe first mobile station (1) are source encoded by a voice encoder (25)according to GSM standard ITU-T G.729 and wherein the useful data in thesecond mobile station (5) are source decoded by a voice decoder (30) inaccordance with the first mobile radio standard.
 7. A method fortransmitting useful data from a first mobile station (1) to a secondmobile station (5), in which for transmission in a firsttelecommunication network (10), the first mobile station (1) encodesuseful data in a first step and then encodes the useful data in a secondstep; the useful data encoded in the first and second steps aretransmitted in the form of a first bit stream to an intermediary station(15) via a transmission channel of the first telecommunication network(10); the useful data encoded in the second step presented in the firstbit stream are decoded by the intermediary station (15); fortransmission in a second telecommunication network (20), the useful dataare channel encoded by the intermediary station (15) and then aretransmitted to a second mobile station (5) via a transmission channel ofthe second telecommunication network (20); signalization data aretransmitted from the intermediary station (15) to the second mobilestation (5), said signalization data containing information regardingthe type of encoding of the useful data in the first step, the usefuldata encoded in the intermediary station are decoded by the secondmobile station (5) and then the useful data coded in the first step aredecoded by the second mobile station (5), according to the signalizationdata received by the second mobile station (5).
 8. The method accordingto claim 7, wherein the useful data encoded in the first and secondsteps are transmitted in the form of said first bit stream to saidintermediary station (15) via at least one third telecommunicationnetwork.
 9. The method according to claim 7, wherein the signalizationdata are added to the useful data coded in the second step and decodedin the intermediary station (15) so that a second bit stream is producedfor transmission in said second telecommunication network (20), theuseful data and the signalization data of the second bit stream areencoded by the intermediary station (15), the useful data and thesignalization data of the second bit stream are transmitted to thesecond mobile station (5) via a transmission channel of the secondtelecommunication network (20), the useful data coded in the second stepand the signalization data of the second bit stream are decoded by thesecond mobile station (5), and the useful data coded in the first step,which are decoded in the second step by the second mobile station (5),are decoded by the second mobile station (5) according to thesignalization data decoded by the second mobile station (5).
 10. Themethod according to claim 7, wherein the useful data in the firsttelecommunication network (10) are transmitted in accordance with afirst mobile standard; the useful data are source encoded and channelencoded in the first and second step, the useful data coded in thesecond telecommunication network are channel encoded and are transmittedin accordance with a second mobile radio standard together with thesignalization data, said signalization data include said informationregarding the type of encoding of the useful data in the first step inaccordance with the first mobile radio standard; and wherein the usefuldata coded in the second step, which are decoded by the second mobilestation (5), are decoded by the second mobile station (5) in accordancewith the first mobile radio standard after evaluating the signalizationdata.
 11. The method according to claim 10, wherein said first mobileradio standard is global system for mobile communications and saidsecond mobile radio standard is universal mobile telecommunicationssystem.
 12. The method according to claim 10, wherein the useful data inthe first mobile station (1) are source encoded by a voice encoder (25)according to GSM standard ITU-T G.729 and wherein the useful data in thesecond mobile station (5) are source decoded by a voice decoder (30) inaccordance with the first mobile radio standard.
 13. The methodaccording to claim 1 or 7, wherein the signalization data aretransmitted from said intermediary station (15) to said second mobilestation (5) singly or multiply via a separate control channel.
 14. Themethod according to claim 1, 3, 7 or 9, further comprising transmittinga telephone number of the first mobile station (1) along with saidsignalization data containing said information regarding said type ofencoding of the useful data in the first step.
 15. The method accordingto claim 1 or 7, wherein said useful data comprises at least one ofvideo data, audio dat, text data and voice data.